Sugar and amino acid intestinal transport systems in land snail Helix aspersa

The intestine of Helix aspersa snail is able to actively transport sugars and amino acids. D-glucose, D-galactose and 3-oxymethylglucose share the same transport system with competitive inhibition between them, which is strictly Na(+)-dependent. Phlorizin has high affinity for that system and inhibits it competitively. D-fructose and L-arabinose are not actively transported, do not inhibit the transport of other sugars, and enter the tissue at a lineal rate with their concentration, which coincides with that of mannitol and with that of actively transportable sugars in the presence of 10(-4)M phlorizin. Galactose seems to enter the tissue from the serosal side through another carrier, with different specificity, Na(+)-independent, inhibited by phloretin but not by phlorizin. There are also transport systems for neutral amino acids, for the basic ones and for imino acids. Neutral amino acids present affinity for the other systems, whereas the basic ones and the imino acids seem to use only those proper to them. The system for imino acids is strictly Na(+)-dependent, but neutral amino acids and the basic ones continue to be transported and accumulated, although to a lesser extent, in the absence of Na+. Transport of sugars and amino acids is scarcely O2 dependent, although it is inhibited by 10(-4)M DNP. It is also partially inhibited by harmaline and by ouabain.